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atmospheric and cloud processes

...nuclei in the atmosphere become effective at supersaturations of around 0.1 to 1 percent (that is, levels of water vapour around 0.1 to 1 percent above the point of saturation). The concentration of
cloud condensation nuclei in the lower troposphere at a supersaturation of 1 percent ranges from around 100 per cubic centimetre (approximately 1,600 per cubic inch) in size in oceanic air to 500 per...

Examples of
cloud condensation nuclei include sodium chloride (NaCl) and ammonium sulfate ([NH
4]
2 SO
2), whereas the clay mineral kaolinite is an example of an ice nuclei. In addition, naturally occurring bacteria found in decayed leaf litter can serve as ice nuclei at temperatures of less than about −4 °C (24.8 °F). In a process called cloud...

biosphere impact on precipitation processes

The formation and subsequent freezing of cloud droplets depend on the presence of
cloud condensation nuclei and ice nuclei, respectively. Significantly, the biosphere is a major source of both of these kinds of nuclei. Over the continents, condensation nuclei are readily available and are of biogenic as well as anthropogenic origin. Examples of condensation nuclei include sea salt, small soil...

As water vapour condenses onto condensation nuclei, the droplets grow in size. Growth proceeds at relative humidity as low as 70 percent, but the rate of growth is very slow. Growth by condensation is most rapid where the air is slightly supersaturated with water vapour. At this point, cloud droplets typical of the size of fog droplets arise. Should temperatures fall to the level where freezing...

weather modification

Cloud droplets form when atmospheric water vapour condenses on small particles in the atmosphere called
cloud condensation nuclei (CCN). Typically, a cloud is composed of tiny spheres of water that range in diameter from a few micrometres to a few tens of micrometres. The number of cloud droplets per cubic centimetre ranges from less than 100 to more than 1,000; 200 droplets per cubic...